Instrument and associated method of trailing for modular hip stems

ABSTRACT

A trial ( 100 ) for use in performing joint arthroplasty is provided. The trial ( 100 ) fits to a cavity ( 103 ) in the canal ( 105 ) of a long bone ( 107 ) and assists in the performing of a trial reduction in performing joint arthroplasty. The trial ( 100 ) includes a stem portion ( 102 ) and a neck portion ( 104 ) fixedly connected to the stem portion ( 102 ) in a plurality of selectable positions with respect to the stem portion ( 102 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

Cross reference is made to the following applications: U.S. patentapplication Ser. No. 10/327,187 entitled “ADJUSTABLE BIOMECHANICALTEMPLATING & RESECTION INSTRUMENT AND ASSOCIATED METHOD”, U.S. Pat. No.7,022,141 entitled “ALIGNMENT DEVICE FOR MODULAR IMPLANTS AND METHOD”,and U.S. Pat. No. 7,235,106 entitled “MODULAR HIP STEMS AND ASSOCIATEDMETHOD OF TRIALING” filed concurrently herewith which are incorporatedherein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of orthopedics, andmore particularly, to an implant for use in arthroplasty.

BACKGROUND OF THE INVENTION

Patients who suffer from the pain and immobility caused byosteoarthritis and rheumatoid arthritis have an option of jointreplacement surgery. Joint replacement surgery is quite common andenables many individuals to function properly when it would not beotherwise possible to do so. Artificial joints are usually comprised ofmetal, ceramic and/or plastic components that are fixed to existingbone.

Such joint replacement surgery is otherwise known as joint arthroplasty.Joint arthroplasty is a well-known surgical procedure by which adiseased and/or damaged joint is replaced with a prosthetic joint. In atypical total joint arthroplasty, the ends or distal portions of thebones adjacent to the joint are resected or a portion of the distal partof the bone is removed and the artificial joint is secured thereto.

There are known to exist many designs and methods for manufacturingimplantable articles, such as bone prostheses. Such bone prosthesesinclude components of artificial joints such as elbows, hips, knees andshoulders.

Currently in total hip arthroplasty, a major critical concern is theinstability of the joint. Instability is associated with dislocation.Dislocation is particularly a problem in total hip arthroplasty.

Factors related to dislocation include surgical technique, implantdesign, implant positioning and patient related factors. In total hiparthroplasty, implant systems address this concern by offering a seriesof products with a range of lateral offsets, neck offsets, head offsetsand leg lengths. The combination of these four factors affects thelaxity of the soft tissue. By optimizing the biomechanics, the surgeoncan provide a patient a stable hip much more resistant to dislocation.In order to accommodate the range of patient arthropometrics, a widerange of hip implant geometries are currently manufactured by DePuyOrthopedics, Inc., the assignee of the current application, and by othercompanies. In particular, the S-ROM® total hip systems offered by DePuyOrthopaedics, Inc. include three offsets, three neck lengths, four headlengths and one leg length adjustment. The combination of all thesebiomechanic options is rather complex.

Anteversion of a total hip system is closely linked to the stability ofthe joint. Improper version can lead to dislocation and patientdissatisfaction. Version control is important in all hip stems. However,it is a more challenging issue with the advent of stems with additionalmodularity.

The prior art has provided for some addressing of the anteversionproblem. For example, the current S-ROM® stems have laser markings onthe medial stem and the proximal sleeve. This marking enables thesurgeon to measure relative alignment between these components. Sincethe sleeve has infinite anteversion, it is not necessarily orientedrelative to a bony landmark that can be used to define anteversion. Infact, the current sleeves are sometimes oriented with the spout pointingdirectly laterally into the remaining available bone.

Prior art stems may be aligned relative to a patient's bony landmarks.These stems are monolithic. They cannot locate the neck independently ofthe distal stem. Therefore, the anteversion is limited. Most bowed,monolithic stems are sold in fixed anteversion; for example, at ananteversion of 15 degrees. These monolithic stems have limitedflexibility for rotational alignment since the distal stem must followthe bow of the patient's femur and this may not provide an operablebiomechanical result.

In a common step in the surgical procedure known as total hiparthroplasty, a trial or substitute stem is first implanted into thepatient. The trial is utilized to verify the selected size and shape ofthe implant in situ on the patient and the patient is subjected to whatis known as a trial reduction. This trial reduction represents movingthe joint, including the trial implant through selected typical motionsfor that joint. Current hip instruments provide a series of trials ofdifferent sizes to help the surgeon assess the fit and position of theimplant. Trials, which are also known as provisionals, allow the surgeonto perform a trial reduction to assess the suitability of the implantand implant's stability prior to final implant selection. In order toreduce inventory costs and complexity, many trialing systems aremodular. For example, in the Excel Instrument System, a product of DePuyOrthopaedics, Inc., there is a series of broaches and a series of necktrials that can be mixed and matched to represent the full range ofimplants. There is a single fixed relationship between a broach and aneck trial, because these trials represent a system of monolithic stemimplants.

Likewise, in the current S-ROM® instrument systems provided by DePuyOrthopaedics, Inc., there are neck trials, proximal body trials, distalstem trials, head trials and sleeve trials. By combining all thesecomponents, the implant is represented. Since the S-ROM stem is modularand includes a stem and a sleeve, the angular relationship or relativeanteversion between the neck and the sleeve is independent andrepresented by teeth mating between the neck and the proximal bodytrial. The proximal body trial has fixed transverse bolts that are keyedto the sleeve in the trialing for straight, primary stems. The long stemtrials do not have the transverse bolts and are thus not rotationallystable during trial reduction and therefore are not always used by thesurgeon.

With the introduction of additional implant modularity, the need forindependent positioning of the distal stem, proximal body and any sleevewhich comprise the implants is required. Currently bowed, monolithicstems are offered with a fixed amount of anteversion, typically 15degrees.

Thus, a need for a prosthetic trial and related implants that providefor anteversion alignment relative to a patient's bony landmark exists.

SUMMARY OF THE INVENTION

Accurate trialing of stem implants is particularly critical withdifficult revision cases. Specifically, since the final axial positionof the distal stem implant is often unknown and not identical to theaxial placement of the distal stem trial, a final check with a trial isan advantage to a surgeon. Although this can be done in some currentsystems, it has not been shown with mechanical key ways that improve theaccuracy of the alignment. According to the present invention, a trialand related surgical method is provided with key ways, teeth, grooves,etc. to provide a mechanical means of communicating mechanicallyalignment information which is considerably more accurate than thestandard method of laser marking and visual recreation. The implanttrials of the present invention allow for accurate measurement andmapping of the rotational position of all components within the trial.

In modular prosthetic stem designs, bowed stems follow the anatomicalcurve of the intermedullary canal of the long bone, and by having amodular stem design, the surgeon is now able to optimize the rotationalposition of all three components. Thus, infinite anteversion of theproximal body implant is possible even when used with bowed distalstems. In addition to standard instrument requirements such asreproducing range of implant sizes and shapes, the present inventiondescribes a trial and a surgical procedure with additional features thatare critical to the functionality of a modular stem implant. These newrequirements include accurate mapping of the relative alignment of necktrials, proximal body trials, distal stem trials and sleeve trials totheir corresponding implant components. The requirements also includeproviding absolute alignment relative to the intramedullary canal and toprovide alignment using mechanical features in addition to standardtechniques using laser markings. Further, the new implant requirementsinclude a new trialing design which is compatible with existing implantswhich clearly expands the value of the new design trial.

The trial of the present invention provides for absolute anteversion ina bowed revision stem. The surgeon may simply use a bowed distal stemtrial to locate the anterior bow of the femur. By utilizing this boweddistal stem trial, the bowed intramedullary canal can be used to defineanteversion anatomically, and the absolute anteversion of a patient'sbone in situ can be dimensioned using these tools of the presentinvention. With the present invention, the bowed intramedullary canal ofthe femur can be used to define anteversion anatomically.

In one aspect, the present invention provides a trial for use inperforming joint arthroplasty. The trial is to be fitted to a cavity inthe canal of a long bone. The trial comprises a stem portion and a neckportion. The neck portion is fixedly connected to the stem portion in aplurality of selectable positions with respect to the stem portion.

In another aspect, the present invention provides a kit for use inperforming joint arthroplasty. The kit comprises a trial and an implant.The trial is for use in performing joint arthroplasty. The trial is tobe fitted to a cavity in the canal of a long bone and to assist inperforming a trial reduction in performing joint arthroplasty. The trialincludes a stem portion and a neck portion selectively operablyconnected to said the portion in a plurality of selectable positionswith respect to the stem portion. The implant is for use in performingjoint arthroplasty. The implant is to be fitted to a cavity in the canalof a long bone and to assist in performing joint arthroplasty. Theimplant includes a stem portion and a proximal body portion selectivelyoperably connected to the stem portion in a plurality of selectablepositions with respect to the stem portion.

In another aspect, the present invention provides a trial for use inperforming total hip arthroplasty. The trial is to be fitted to a cavityin the femoral canal of a femur and is provided to assist in performinga trial reduction in performing joint arthroplasty. The trial comprisesa stem portion and a neck portion. The stem portion defines alongitudinal axis. The neck portion is selectively rotatably connectedto the stem portion and fixedly connectable in plurality of selectablepositions with respect to the stem portion about the longitudinal axisof the stem portion.

In another aspect, the present invention provides a kit for use inperforming hip joint arthroplasty. The kit comprises a trial and animplant set. The trial is for use in performing joint arthroplasty; thetrial is to be fitted to a cavity in the canal of a long bone and toassist in performing a trial reduction in performing joint arthroplasty.The trial includes a stem portion and a neck portion selectivelyoperably connected to the stem portion in a plurality of selectablepositions with respect to the stem portion. The implant set includes aplurality of proximal bodies and distal components. An implantableimplant is to be selected from one of the proximal bodies and one of thedistal components. The implantable implant is to be positioned in thecavity of the long bone, so that the proximal body and the distalcomponent can be assembled to form a hip femoral component assemblywithout the removal of the distal component from the cavity and so thatthe implantable implant can be assembled from said implant set.

In another aspect, the present invention provides a method for providingjoint arthroplasty. A long bone is resected. A cavity is prepared in themedullary canal of the long bone. A trial is provided. The trial has astem portion and a neck portion adjustably, fixedly connected to thestem portion in a plurality of selectable positions with respect to thestem portion. The stem portion has a feature to cooperate with a bonylandmark of the patient. One of a plurality of selected positions isselected. A trial reduction is performed using the trial. The optimumposition of the neck portion with respect to the stem portion isdetermined. An implant is selected with the optimum position of the neckportion with respect to the stem portion. An implant is selected withthe optimum position of the neck portion with respect to the stemportion. A selected implant is implanted in the cavity.

In another aspect, the present invention provides a method for providingjoint arthroplasty comprising resecting a long bone and preparing acavity in the medullary canal of the long bone. A trial is providedhaving at least two portions; the two portions are rotatable withrespect to one another. An implant is provided having at least twoportions; the two portions are rotatable with respect to one another. Atool is also provided. The tool, the portions of the trial and theportions of the implant have mating keys and keyways for determining therelative rotational position of said portions of said trial and saidimplant.

In another aspect, the present invention provides a method for providingjoint arthroplasty wherein the joint includes a long bone having a bowand a neck and an intramedullary canal having a bow. The methodcomprises determining the position of a plane through the bow andintramedullary canal of the long bone and determining the anatomicanteversion angle from the position of the plane of the bow and theposition of the neck. A trial is provided having a stem portion and aneck portion adjustably, fixedly connected to the stem portion in aplurality of selectable positions with respect to the stem portion. Thestem portion has a bow to fit in the bow of the intramedullary canal.The neck portion is positioned on the stem portion at a trialanteversion angle based upon the anatomic anteversion angle. An implantis provided having a stem portion and a proximal portion adjustably,fixedly connected to the stem portion in a plurality of selectablepositions with respect to the stem portion. The stem portion has a bowto fit the bow in the intramedullary canal. The proximal portion of theimplant is positioned on the stem portion of the implant at a prostheticanteversion angle based upon the trial anteversion angle.

The technical advantages the present invention include the ability ofthe trials of the present invention to be used such that a distal stemimplant may be placed in situ and the proximal body trial and neck trialbe placed on the distal stem implant. This combination of distal stemimplant and proximal body trial may be accomplished without damaging thelocking taper on the distal stem implant or to require the removal ofthe distal stem implant. For example, according to one aspect of thepresent invention, the trial includes a distal stem trial and a proximalbody trial. The proximal body trial can be used with both the distalstem trial and the distal stem implant, and trialing of the proximalportion can be accomplished with the distal stem implant in situ. Thus,the present invention provides for mixing of components which are trialcomponents of the present invention and implant components.

The technical advantages of the present invention further include theability of the trial of the present invention to provide absolute andrelative rotational alignment of all components including the proximalbody, distal stem, neck and the sleeve. Rotational alignment can bebased on the position of the stem in the intramedullary canal of thelong bone.

The technical advantages of the present invention further include theability to translate the rotational position of the distal stem as farproximal as possible. For example, according to one aspect of thepresent invention, the proximal body trial is keyed to the distal stem.Thus, the present invention permits the position of the proximal body ofthe trial to be a substitute for the relative position of the distalstem trial or implant.

The technical advantage of the present inventions also include theability of either the trial sleeve or the implant sleeve to haveinfinite rotation. For example, according to one aspect of the presentinvention, the sleeve is fitted with an internal taper over an externaltaper on the proximal body of the trial or implant. The connectionbetween the proximal body trial and a sleeve is a slip fit. Theconnection between the proximal body implant and a sleeve is a taperlock. Thus, the present invention provides for the proximal body trialto have an absolute angular measurement of this sleeve for accuratealignment of the stem in the intramedullary canal and to the neck axis.

The technical advantage of the present invention further includes theability to align the implant or trial either on the back table or insitu in the patient. For example, according to one aspect of the presentinvention, the surgical technique provides for an instrument to be usedwith the implant and the trial such that the proper orientation of theimplant can be determined based upon the discovered and fine-tunedposition of the trial found in situ on the patient or through CT scans,radiographs, or other imaging techniques. Thus, the present inventionprovides for a surgical technique that allows rotational alignment to bemapped from instruments to implants either on the back table or in thebone.

Another technical advantage of the present invention is that the angularposition can be dialed or determined by use of a cervix coupling orteeth which may be rotated with a click type feel every, for example,ten degrees. For example, according to one aspect of the presentinvention, the trial includes mating gears which form a cervix couplingbetween the proximal body trial and the neck trial to assist indetermining the relative position of the neck to the distal stem. Thus,the present invention provides simple anteversion adjustment without theneed to view any marks on the prosthesis.

The technical advantages of the present invention further includes theadditional safety of a combination of a threaded engagement and atapered fit for the implants. For example, according to one aspect ofthe present invention, the trials of the present invention, provide fora slip fit between the distal stem and the proximal body trial and a nutcontained within the neck trial which may be engaged with an externalthread on the proximal end of the distal stem. Thus, the presentinvention provides for two well proven forms of connections to providefor a secure connection of the proximal body and neck to the distalstem.

A further technical advantage of the present invention includes a quickconnect option to improve the ergonomics and provide immediate feedbackon leg length prior to trial reduction. For example, according to oneaspect of the present invention, the proximal body includes a springtype clip to hold the proximal body in position against the distal stemwithout any nuts or locked tapered engagement. Thus, the presentinvention provides for a quick connect option to improve ergonomics andprovide immediate feedback on leg length prior to trial reduction.

A further technical advantage of the present invention is the ability ofthe trials of the present invention to be compatible with monolithicstems as well as with modular stems. Thus, for example according to oneaspect of the present invention, the trials may be sized to match withexisting monolithic implants as well as with modular prosthesis. The useof the trials that work with modular as well as with monolithic implantsminimizes complexity of the instrumentation, duplication, and reducesthe quantity of inventory required. For example, according to one aspectof the present invention, the implant of the present invention may workfor both monolithic and modular prosthesis. Thus, the present inventionprovides for a trial that works with both monolithic and modular stemimplants.

Other technical advantages of the present invention will be readilyapparent to one skilled in the art from the following figures,descriptions and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of a modular trial in accordance with anembodiment of the present invention;

FIG. 2 is a partial plan view of the modular trial of FIG. 1;

FIG. 3 is an exploded cross-sectional view of the modular trial of FIG.1;

FIG. 4 is a partial exploded cross-sectional view of the modular trialof FIG. 1;

FIG. 4A is a partial exploded cross-sectional view of the modular trialof FIG. 1 showing the index mechanism in greater detail;

FIG. 5 is a partial perspective view of proximal portion of the modulartrial of FIG. 1;

FIG. 6 is a partial cross-sectional plan view of the modular trial ofFIG. 1;

FIG. 7 is a partial plan view of the modular trial of FIG. 1;

FIG. 8 is a/partial cross-sectional view of the modular trial of FIG. 1;

FIG. 9 is a partial cross-sectional view of the modular trial of FIG. 1;

FIG. 10 is a side view of the modular trial of FIG. 9;

FIG. 11 is a top view of the modular trial of FIG. 1;

FIG. 12 is a plan view of a first embodiment of a modular hip stem foruse in the medullary canal of a femur which may be used with the trialof the present invention to practice the surgical method of the presentinvention;

FIG. 13 is an exploded view of the hip stem of FIG. 12;

FIG. 14 is a partial perspective view of the modular hip stem of FIG. 12showing the keying slot;

FIG. 15 is a partial top view of the stem of FIG. 12 showing the keyingslot;

FIG. 16 is a perspective view of a femur, from the proximal end of thefemur, illustrating a plane through the bow of the femur;

FIG. 16A is a cross-section of the femur of FIG. 16;

FIG. 17 is a top view of the stem of FIG. 12;

FIG. 18 is a plan view partially in cross-section of the modular hipstem of FIG. 20 showing the distal stem portion in greater detail;

FIG. 19 is a side view partially in cross-section of the modular hipstem of FIG. 20;

FIG. 20 is a plan view of another embodiment of a modular hip stem whichmay be used with the trial of the present invention to practice thesurgical method of the present invention;

FIG. 21 is an exploded view of the hip stem of FIG. 20;

FIG. 22 is a perspective view of the modular hip stem of FIG. 20 showingthe implant in a femur;

FIG. 23 is another perspective view of the modular hip stem of FIG. 20showing the stem in a femur;

FIG. 24 is a perspective view of an alignment tool that may be used toregister the alignment of the modular trial of FIG. 1 or the hip stemsof FIGS. 12 and 20 shown in position on the modular trial forregistering the alignment the modular trial of FIG. 1;

FIG. 25 is a side view of the alignment tool of FIG. 24;

FIG. 26 is a cross-sectional view of FIG. 25 along the line 26-26 in thedirection of the arrows;

FIG. 27 is a perspective view of the alignment tool of FIG. 24 inposition on the trial of FIG. 1;

FIG. 28 is a partial perspective view of FIG. 25 showing the keyedtiming of the distal stem of the trial and/or distal stem implant withthe alignment tool;

FIG. 29 is a partial perspective view of FIG. 27;

FIG. 30 is a top view of FIG. 27;

FIG. 31 is a perspective view of the alignment tool of FIG. 24 inposition on the implant of FIG. 20;

FIG. 32 is a perspective view of an alternate embodiment of an alignmenttool that may be used to register the alignment of the modular trial ofFIG. 1 or the hip stems of FIGS. 12 and 20 shown in position on themodular trial for registering the alignment the modular trial of FIG. 1;

FIG. 33 is a partial perspective view of FIG. 32 showing the keyedtiming of the distal stem of the trial with the alignment tool;

FIG. 34 is a perspective view of the distal stem of the modular hip stemof FIG. 20 in a femur with a neck and proximal body trial of FIG. 1;

FIG. 35 is a plan and perspective view of a kit for use in arthroplastyaccording to the present invention; and

FIG. 36 is a process flow chart for a method of performing jointarthroplasty surgery according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention and the advantages thereof are bestunderstood by referring to the following descriptions and drawings,wherein like numerals are used for like and corresponding parts of thedrawings.

Referring now to FIG. 1, a trial 100 is shown for use in arthroplasty.Often orthopedic surgeons utilize trials such as the trial 100 to placea substitute prosthetic item in the patient's body that can be removedafter the trialing or prior to the final selection of the prosthesis.Once the dimensions of the trial are verified through reduction ormovements of the patient's leg through the typical motion that a patientwill require, the trial is removed and is sterilized for later use inother surgeries. Conversely, a prosthetic implant, once exposed to apatient, is not utilized again. Therefore, it is important the shape,position and location of the appropriate trial be exactly duplicated bythe actual implant. The trial 100 is utilized for performing jointarthroplasty. The trial 100 is adapted to be fitted to a cavity 103 inthe canal 105 of a long bone 107. The trial 100 is utilized to assist inperforming a trial reduction for joint arthroplasty. The trial 100includes a stem portion 102 and a proximal body portion 114 fixedlyconnected to the stem portion 102 in a plurality of selectable positionswith respect to the stem portion 102.

The stem portion 102 may define a longitudinal axis 104 of the stemportion 102. The neck portion 106 defines an opening 109 therein. Theopening 109 defines a longitudinal axis 111 of the neck portion 106 andthe proximal body portion 114. The longitudinal axis 111 of the opening109 is preferably coincident with the longitudinal axis 104 of the stemportion 102. The neck portion 106 is rotatably connected to the proximalbody 114 about the longitudinal axis 104 of the stem portion 102.

The distal stem assembly 102 may include a proximal stem portion 108,which is connected to a curved distal stem portion 110. The proximalstem portion 108 and the curved distal stem portion 110 may be integralor, as shown in FIG. 1, the curved distal stem portion 110 may include aprotrusion 112 which mates with a cavity 113 in the proximal stemportion 108. A pin 116 may be used to connect the proximal stem portion108 to the curved distal stem portion 110.

Referring now to FIGS. 2 through 10, preferably the neck trial 106 isconnected to the distal stem assembly 102 in such a way that the angularposition along centerline 104 between the neck trial and the distal stemmay be adjusted. For example, as shown in FIGS. 2 through 10, theproximal body trial 164 may include an index mechanism 120 that permitsa fixed degree of rotational adjustment between the neck trial 106 andthe distal stem assembly 102. Referring to FIGS. 4 through 8, the indexmechanism 120 may include first gear or spline 122. The index mechanism120 may also include a second spline or gear 124 which meshes in and outselectively of engaging with the first gear 122. The second spline orgear 124 may, as shown in FIG. 4, be integral with the neck trial 106.It should be appreciated that optionally the second gear 124 may be aseparable component fixably secured to the proximal body 106. The gears122 and 124 each have a plurality of teeth 136. Each tooth issubstantially the same as all other teeth 136. The teeth 136 of each ofthe gears 122 and 124 are virtually the same. The teeth 136 are spacedequally radially around the centerline 104 of the stem. When the teeth136 of, for example, the first gear 122 are rotated one (1) toothrespect to the second gear 124, the first gear 122 is rotated byrelationship which comprises: 1 divided by the number of teeth on agear, times 360 degrees.

Thus, for a first gear 122 and a second gear 124, each having 36 teeth,the single index of the first gear 124 provides for a 10 degree relativemotion of the first gear 122 with respect to the second gear 124. Asshown in FIG. 4, when the first gear 122 is moved in the direction ofarrows 133 toward the second gear 124, the gears 122 and 124 may belocked into engagement. Similarly, when the first gear 122 and thesecond gear 124 are moved away from each other in the opposite directionof arrows 133, the neck trial 106 is permitted to rotate with respect tothe stem 102. Thus, the index mechanism 120 may provide for 36 differentrelative positions to the neck trial 106 with respect to the distal stemassembly 102 when the gears 122 and 124 each contain 36 teeth.

Any of a variety of mechanisms may be used to engage and disengage thegears or splines 122 and 124 with each other. Preferably, and as shownin FIGS. 4 and 4( a), the gears or splines 122 and 124 are selectivelyengaged and disengaged by means of a spring 150 which is used to gentlyurge the first gear 122 into engagement with the second gear 124. Whenthe stem 102 is placed in position in the neck trial 106, the stem 102includes a circular rib 152 which when the stem 102 is fully engagedinto the neck trial sandwiches the spring 150, the first gear 122 andthe second gear 124, and the proximal body trial 114 between the rib 152and an annular shoulder 153 on the stem 102 which mates with nut 158.

Preferably, the location of the rib 152 and the shape and size of thespring 150 are designed such that the spring 150 is sufficient to gentlyengage the first gear 122 in mesh with the second gear 124. The spring152, however, is weak enough to permit the gentle indexing of the necktrial 106 relative to the stem 102 to provide easy adjustment of theanteversion angle. Once the proper anteversion angle has beendetermined, the neck trial 106 needs to be firmly and securely engagedwith the stem 102.

Preferably, and as shown in FIG. 4, the proximal end of the stem 102includes external threads 162 that engage with connector nut 126.Referring to FIGS. 4 and 5, the trial 100 may include the proximal bodytrial 114, which is comprised of a sleeve 164 that slidably fits overthe stem 102. The proximal end of the sleeve 164 includes internalthreads 166 that mate with external threads 176 on the keyed component156. As shown in FIG. 5, the keyed component 156 has a central opening168 with opposed flats 170. Similarly, the keyed component 156 has asecond timing feature (not shown) that cooperates with a locationfeature (not shown) on the spline member. The location features on thekeyed component 156 and the first gear 122 cooperate to permit the firstgear 122 to move axially in the direction of centerline 104 but preventrotation of the first gear 122 with respect to the keyed component 156.A ring 174 is slidably fitted over the outer diameter 177 of the keyedcomponent 156. The ring 174 is permitted to freely rotate with respectto the spline member 172 and the keyed component 156. The keyedcomponent 156 is assembled by threadably engaging into the sleeve 164causing the spline member 172 and ring 174 to be trapped there between.

Although the keyed member 156, spline member 172, ring 174 and sleeve164 can be supplied to the surgeon as individual components, they canalso be preassembled before being supplied to the surgeon, therebysaving the surgeon the time of assembling these components in theoperating room. The assembly of the keyed member 156, spline member 172,ring 174 and sleeve 164 is designated the proximal body portion 114 inthe drawings and in this description.

When the proximal body trial assembly 114 including the sleeve 164, thering 174, the spline 172 and the keyed component 156 are sandwichedbetween the stem 102 and the neck trial 106, the connector 126 is thenthreadably engaged into the external threads 162 of the stem 102. Untilthe connector nut 126 is fully torqued onto the stem 102, the ring 174is free to rotate about centerline 104. Until the connector nut 126 issecurely torqued against the stem 102, the neck trial 106 may be freelyrotated with only the resistance of the spring 150 in the direction ofarrows 178 to permit the adjustment for anteversion for the trial 100.To assist in permitting and torquing of the connector nut 126, theconnector nut 126 may optionally have external splines or knurls 180.Referring to FIG. 6, the connector nut 126 may be permanently secured tothe proximal body 106 by means of a pin 182 in the neck trial 106. Whenthe pin 182 traps the connector nut 126 within the neck trial recess184, the pin 182 limits motion of the connector nut 126 to within thatof the connector nut groove 186.

Optionally, as shown in FIG. 5, the trial 100 may include an outer trialsleeve 130 that is used to replicate a prosthetic sleeve once theproximal body trial is loaded onto the distal stem. This sleeve 130 maybe secured to this distal stem assembly by inner sleeve 164 which formsa slip fit with the tapered bore 136 of the outer sleeve 130.

Referring now to FIG. 10, the curved distal stem portion 110 is shownwith the curved distal stem 110 showing the full extent of the curve.The curved distal stem portion 110 may be defined, by example, a radiusRR extending from an origin 00. The radius RR may be, for example, 4 to8 inches, and may vary depending on the curvature of the patient'sfemoral intramedullary canal.

Referring now to FIG. 2, the neck trial portion 106 of the trial 100 mayinclude a neck 140 to which a ball or head 133 may be used to fitagainst an acetabular cup (not shown) on the acetabulum of the patient.

Referring now to FIGS. 1 and 11, the trial 100 preferably includeslocating features to determine the relative angular position ααα betweenthe neck centerline 142 and the stem centerline 144. For example, theneck trial 106 may include a body locating feature 146 while the distalstem assembly 102 may include a stem locating feature 148. The necktrial's locating feature 146 may be in the form of, for example, opposedcylindrical holes. The stem locating feature 148 may be, for example, inthe form of a key way or oval-shaped slot in the proximal end of thedistal stem assembly 102.

Preferably, so that the trial may be used with a variety of hip stems,the holes 146 should be used as a standard for those prostheses to whichthe trial is associated. Similarly, the slot 148 of the trial 100 shouldpreferably be replicated in any prosthesis to which the trial of thepresent invention is to be used as a system. Preferably, in order thatthe position of the outer sleeve 130 may be replicated or measuredduring the trialing of a hip stem prosthesis utilizing the trial 100,the trial 100 includes pins 190 located in opposed directions on ring174. The pins 190 are radially fitted to opposed slots 192 located onthe outer sleeve 130. As the outer sleeve 130 is positioned in theproper location to properly anchor the trial 100, the angular positionof the outer sleeve 130 can be locked and its position recorded by thetightening of the connector nut 126. When the connector nut 126 issecured against the stem 102, the spline member 172 and sleeve 164 placean axial load against the faces 194 of the ring 174, locking it into afixed angular position, thus locking the construct comprised of the necktrial 106, stem trial 102 and outer sleeve trial 130. The outer sleeve130 is thereby locked into an angular position that may be duplicatedlater on an implant.

Referring now to FIGS. 12 through 19, an alternative modular hip implantembodiment is shown which may be used in conjunction with the trial 100of the present invention to accomplish a method of trialing according tothe present invention. The hip stem 10 is suitable for use with theillustrated trial 100 or with other embodiments of such a trial. The hipstem 10 may be made of any suitable durable material that is compatiblewith the human body. For example, the hip stem 10 may be made of atitanium alloy, a cobalt chromium alloy, or a stainless steel. As shownin FIGS. 12 through 19, the hip stem 10 includes a proximal body 12 andbowed distal stem 14.

Referring now to FIG. 18, the proximal body implant 12 may be secured tothe distal stem 14 in any suitable fashion. For example, and as shown inFIG. 18, the proximal body 12 may be secured to the distal stem 14 bymeans of threads 15 located on the proximal portion of the proximal body12, which are threadably engaged to a nut 16. In addition and as shownin FIG. 18, the distal stem 14 may include an external tapered portion18 which mates with an internal tapered portion 20 of the proximal body12. The taper of the internal tapered portion 20 and the externaltapered portion 18 may be defined by an angle φ. Preferably, the taperis self-locking and has an angle φ of, for example, approximately 18degrees or less.

Referring now to FIG. 13, the proximal body 12 and the distal stem 14may either or both be rotatable around longitudinal centerline 22. Forexample, the proximal body 22 may be rotatable in the direction ofarrows 24 and the distal body may be rotated in the direction of arrows26.

Referring now to FIGS. 16 and 16A, a patient's femur is shown at 27. Thenatural femur 27 has an anatomical anteversion. As shown in FIG. 16, thenormal femur is bowed anteriorly. In the present invention, theanatomical anteversion angle α is defined by a plane, shown at 29 inFIGS. 16 and 16A, through the anterior bow 31 of the femur, and a linethrough the center of the femoral neck, shown at 33 in FIGS. 16 and 16A.The plane 29 corresponds with the position of the intramedullary canal.Since the stem of the prosthesis will be received in the intramedullarycanal, in the present invention, the anatomical anteversion of the femurcan provide the basis for setting the prosthesis anteversion. In thefollowing description and in the drawings, the reference a is used forthe anatomical anteversion angle as defined above; the reference αα isused for the prosthetic or assembly anteversion angle. The prosthetic orassembly anteversion angle is defined by a plane through the bowed stemof the prosthesis and a line through the neck of the proximal part ofthe prosthesis. In at least one aspect of the present invention, a trialanteversion angle ααα between a plane through the stem and the neck ofthe trial can be based on data gathered preoperatively and can beadjusted by the surgeon intraoperatively to adjust the trial; thesurgeon can use this data to assemble the modular prosthetic implant.Such a trial anteversion angle is illustrated in FIG. 11. Thus, throughuse of the present invention, the surgeon should be able to assemble aprosthesis such that the prosthetic or assembly anteversion angle ααapproximates the anatomical anteversion angle α. However, it should beunderstood that other landmarks could be used to determine the anatomicanteversion angle, and unless expressly called for in the claims, thepresent invention is not limited to any particular reference for theanatomic anteversion angle. For example, the anatomic anteversion anglecould be determined from the position of the patient's foot with respectto the patient's shoulder line. It should also be understood that theprinciples of the present invention could also be applied to otherprosthetic joints, such as shoulders, and the reference for the anatomicanteversion angle will depend on anatomic features of the bonescomprising that joint. In addition, because of factors such as placementof the acetabular component of the prosthetic implant, the surgeon maydetermine that the optimum prosthetic anteversion angle αα should varysomewhat from the anatomic anteversion angle α. With the presentinvention, the surgeon can make such adjustments intraoperatively.

Referring now to FIG. 17, the angular position between the neck 32 ofthe proximal body and the distal curved portion 34 of the curved distalstem 14 form the prosthetic anteversion angle αα. The anteversion angleαα affects the patient's ability to function and the patient's gait.

As shown in FIG. 13, the hip stem 10 includes a proximal body locationfeature in the form of holes 36. It should be appreciated that the holes36 should be designed of the same shape and location as the holes 146 ofthe trial 100. Similarly, the distal stem includes a distal stemlocation feature in the form of, for example, a slot 38. It should beappreciated that the slot 38 should be made compatible and have the samesize and shape as the slot 148 of the trial 100. The proximal bodylocation feature 36 and the distal stem location 38 may have anysuitable shape and may be in the form of, for example, slots, indents,triangles, squares, polygons or any indexable feature.

Referring to FIGS. 14 and 15, the slot 38 is shown in greater detail. Asshown in FIG. 15, the slot 38 may include two arcuate portions 39defined by radius R extending from center points 40. The center points40 may be spaced from each other a distance, for example, A. The slotmay have a depth T of, for example, 0.1 to 0.7 inches. Referring now toFIG. 19, the distal stem 14 is shown in location where the arcuate theshape of the distal stem is most pronounced. The curvature of the distalstem 14 may be defined by a radius R extending from a distal stem centerpoint 42. The distal arcuate stem 14 is fitted into arcuate portion 44of the medullary canal 46 of the femur 48. The distal stem 14 mayfurther include a slot 50 to assist in the positioning of the arcuatefemur 48 into the arcuate medullary canal 46 of the femur 48.

Referring now to FIGS. 20 through 23, another embodiment of the hip stemfor use in a hip prosthesis that may utilize the trial and surgicalprocedure of the present invention is shown. Hip stem assembly 50includes stem 54. The stem 54 includes a proximal body 52 and a distalstem 54. Like the stem 10 of FIG. 12, the proximal body 52 of the stem54 may be secured to the distal stem 54 through an internal taper 62 inthe proximal body 52, which is mateable with the external taper 60 onthe distal stem 54. It should be appreciated that the tapers 60 and 62are preferably self-locking as in the stem 10. A ball or head 58 thatmates with a cup (not shown) secured to an acetabulum (not shown) may belocated on the proximal body. The distal stem 54 and the proximal body52 may further be secured to each other by means of, for example, a nut56 that is threadably engaged to a threaded portion 59 of the distalstem 54. Similar to the stem 10 of FIGS. 12 through 19, the stem 54includes a first location feature 66 associated with the distal stem 54and a second alignment feature 53 associated with the proximal body 52.

The first alignment feature may be in the form of a recess 66 with afeature that can transmit torque. For example, the first alignmentfeature 66 may be in the form of a triangular opening, a rectangularopening, a philips screw slot, a screw slot, or as shown in FIG. 22, inthe form of a oval slot. The slot 66 of the stem 54 may be made tosimilar dimensions to that of slot 38 of the hip stem 10.

The hip stem 54 may include, in addition to the components alreadymentioned, a sleeve 72 that may mate with the proximal body 52. Thesleeve 72 may include a bore with an internal taper 74 which mates withthe external taper 76 on the proximal body 52. The sleeve 72 serves toprovides additional support for the prosthesis 51 in the metaphysealregion and provides increased stability for the prosthetic stem 54 whenthe stem receives torsional loads.

The second alignment feature 53 may be in the form of a pair of postholes that are similar to the holes 36 of the hip prosthesis 10.

Referring now FIGS. 22 and 23, the hip stem assembly or construct 51 isshown in position in the long bone or femur 48. The proximal body 52 isshown in position with the neck 80 and the bowed portion 82 of thedistal stem 54 being out of angular alignment. The angle between theneck 80 and the arcuate portion 82 is defined by prosthetic anteversionangle αα. It should be appreciated that in FIGS. 20 and 21, the distalstem 54 is out of angular position with respect to neck.

Referring now to FIG. 24, an instrument 200 is shown for use with thetrial 100 of the present invention as well as with the stem 10 and thehip stem 51 to perform the surgical procedure of the present invention.The instrument 200 may be utilized with either implants or trials. Forexample, the instrument 200 may be utilized with the trial 100 of FIGS.1 through 11, or with the hip stem 10 of FIGS. 12 through 19. Likewise,the instrument 200 may be used with the hip stem 51 of FIGS. 20 through23.

The instrument 200 is used in conjunction with the relative angularorientation of a first component of a multi-piece prosthesis to a secondcomponent of a multiple piece prosthesis. The instrument 200 may beutilized to observe the relative angular orientation of the componentsand to replicate the angular orientation of the first component relativeto the second component. While the instrument 200 may be adapted for anyof a large number of designs of prosthetic components and prosthetictrial components, including the hip stem 10, the hip stem 51 and thetrial 100, the instrument 200 will for simplicity now be described foruse with the hip stem 51 of FIGS. 20 through 23.

Continuing to refer to FIG. 1, the instrument 200 is utilized for atleast one of observing or replicating the relative angular orientationof a first component, for example, proximal body 52 of the prosthesiswith respect to a second component, for example, hip stem 54 of theprosthesis for use in joint arthroplasty.

The instrument 200 includes a first member 202 for cooperation with thefirst component 52. The second member 202 may have any suitable size andshape capable for cooperation with the first component 52. As shown inFIG. 24, the first member 202 may include a first member keyed feature204. The first member keyed feature 204 cooperates with a firstcomponent keyed feature, for example, slot 66 of the first component 54.The keyed features 204 and 66 are used to angularly link the firstmember 202 with the first component 54.

The keyed features 204 and 66 may have any suitable size and shape suchthat the first member 202 and the first component 54 are in timedengagement to provide a rotational linkage of the first member 202 tothe second component 54 about longitudinal centerline 206 of theinstrument 200. The first keyed feature 204 may be in the form, forexample, of a recess or, as shown in FIG. 1, in the form of aprotrusion. For cooperating with, for example, the slot of the hip stem50, the keyed feature 204 may be in the form of an oval protrusion. Itshould be appreciated that the keyed feature 204 may be a recess or aprotrusion or may be square, triangular, rectangular, a polygon, or anyshape capable of transmitting torque.

The instrument 200 further includes a second member 210 for cooperationwith the first component 52. The second member 210 may be in cooperationwith the second component 52 in any suitable manner. For example, thesecond member 210 may include a second member keyed feature 212, whichcooperates with, for example, the second component keyed feature in theform of holes 53. The second member keyed feature 212 may have anysuitable form and may, for example, be in the form of a pin 212, a flap214, an arm 216, or in the form of a yoke (not shown).

For the instrument 200 to cooperate with the holes 53 in the hipprosthesis 50, the instrument 200 includes the pin 212 extendinginwardly from the arm 216. To enhance the stability of the instrument200, the instrument 200 may further include a stabilizing member 218similar to the second member 210, but being a mirror image of the secondmember to attach to the opposite side of the second component. Thestabilizing member 218 also includes the arm 216, pin 212 and the flap214.

Continuing to refer to FIG. 24, the instrument 200 further includes afeature 220 for cooperation with the first member 202 and the secondmember 210 for at least one of replicating or observing the relativeangular orientation of the first component with respect to the secondcomponent 52. The feature 220 may be in the form, for example, a body.At least one of the first member 202 and the second member 210 aremovably connected to the body 220. The body 220 serves the purpose ofoperably interconnecting the first member 202 to the second member 210.With the use of the body 200, the first member 202 may be positionedappropriate relative to the second member 210 to replicate or observethe relative angular orientation of the first component 54 with respectto the second component 52.

For example, and as shown in FIG. 24, the body 220 may include alongitudinal opening 222 into which an orientation rod 224 is slidablymovable along longitudinal axis 206. The first member keyed feature 204may be located on an end of the orientation rod 224. The orientation rod224 may include a gripping feature 223 in the form of, for example,flaps or splines for assisting in attempting to move the orientation rod224 axlely along the longitudinal centerline 206 and to rotate theorientation rod 224 in the direction of arrows 226.

As shown in FIG. 24, the orientation rod 224 and the keyed feature 204may be angularly oriented with respect to the body 220 electivelypermitting and preventing the orientation rod 224 from rotating in thedirection of arrows 226. Such selective rotation of the orientation rod224 may be accomplished by any method.

For example, the body 220 may include a locking arm 228 connected to acam 230 by shaft 232 mounted to the body 220. The cam 230 may utilizedto selectively lock the orientation rod 224 in a fixed position withrespect to the body 220 or, as shown in FIG. 24, may merely prevent theorientation rod from rotating in the direction of arrows 226.

In order that the locking arms 228 may be utilized to prohibit rotationin the direction of arrow 226 while permitting the movement of theorientation rod 224 along the axis of the longitudinal centerline 226,the body 220 may further include a bushing or sleeve 234. The sleeve 234is rotatably fitted to the opening 222 in the body 220. The cam 230selectively engages the sleeve 234 to prevent and permit relative motionof the sleeve 234 with respect to the body 220. The sleeve 234 may beoperatively connected to the orientation rod 224 such that theorientation rod 224 may move along the longitudinal axis 206 butprohibit it from relative motion with respect to the sleeve 234rotationally in the direction of arrow 226.

One method, as shown in FIG. 1, of preventing rotation of theorientation rod 224 with respect to the sleeve 234 is by providing, forexample, a longitudinal groove in the orientation rod 224 thatcooperates with a protrusion 240 extending inwardly from the sleeve 234.To keep the keyed feature 204 of the orientation rod 224 in fullengagement with the slot 66 of the hip prosthesis 50, the instrument 200may include a spring 242 positioned between the orientation rod 224 andthe body 220 towards the orientation rod 224 and the keyed feature 204downwardly in the direction of arrow 244.

As shown in FIG. 24, the second member 210 is rotatably fixedly securedto the body 220 about the longitudinal axis 206. To assure that the pin212 is fully engaged in hole 53 of the prosthesis 50, the arm 216 may,as shown in FIG. 24, pivot about pin 246 secured at hole 248 of the body220. Similarly, the stabilizing member 218 engages the other hole 53 offirst component 54 at pin 212 and is pivotably positioned with respectto the body 220 at pin 246 secured to hole 248 in the body 220. Thesecond member 210 and the stabilizing member 218 are preferably urged inthe direction of arrows 250 toward the second component 52 by means ofsprings 252 positioned between the arms 216 and the body 220.

To measure the relative position of the first member 202 with respect tothe second member 220 and correspondingly, the relative angular positionof the first component 54 to the second component 52, the instrument 200may include indicia 254 located on the instrument 200 providingmeasuring scale for the relative position of the first member 202 withrespect to the second member 210.

The indicia 254 may have any suitable size and shape capable ofproviding the measurement capability for the instrument 200. The indicia254 may, for example, include a single indicia in the form of a mark 256extending axlely along orientation rod 224. The indicia 254 may furtherinclude a plurality of indicia in the form of body indicia 260 locatedon the sleeve 234 of the body 220. Numbers 262 may be located adjacenttheir respective body indicia 260. The numbers 262 may correlate to, forexample, a particular degree of anteversion.

Referring now to FIGS. 27 through 30, the trial 100 of the presentinvention is shown with the instrument 200 in position on the trial 100.The instrument 200 is secured in position on the trial 100. The pins 212on the arm 216 are engaged in the holes 146 of the proximal body 106 ofthe trial 100. Similarly, the key 204 of the orientation rod 224 of theinstrument 200 is engaged in slot 146 of the stem assembly 102 of thetrial 100. By loosening the nut 126 from the stem assembly 102, theproximal body 106 may rotate in the direction of arrows 226 with respectto the distal stem assembly 102. Stem center plane 144 and the neckcenter plane 142 define an included β of the trial 100.

By radiograph, CT scan or other imaging techniques, a patient's anatomicanteversion angle α may be determined. In typical cases, this anatomicanteversion angle α will be the optimum prosthetic anteversion αα. Thetrial 100 may be set by the instrument 200 so that the trial anteversionangle ααα equals the optimum anteversion angle of, for example, 90degrees. Once the optimum trial anteversion angle ααα has beendetermined and set, the nut 126 may be tightened onto the distal stemassembly causing the index mechanism 120 to securely lock. Once securelylocked, the index mechanism may prevent the rotation of the neck 140with respect to the distal stem assembly 102.

It should be appreciated that the indicia 254 on the instrument 200 maybe utilized either to save predetermined anteversion angle determined byradiograph, CT scan, or other imaging technique, or by a common presetanteversion angle. It should be appreciated by utilizing the instrument200 and the trial 100, the proximal body 106 may be rotated with respectto the distal stem 102 an increment based on the index mechanism 120 ofperhaps 10 degrees or less.

For example, the trial 100 may be preset utilizing instrument 200 to aparticular first trial anteversion angle ααα. The trial 100 may then beinserted into a patient and a trial reduction performed. If the trialreduction indicates that the trial anteversion angle ααα should beincreased or decreased, the nut may be loosened enough to permitrotation of the index mechanism 120 and the proper amount of change ofanteversion can be set by utilizing the indicia 254 and the instrument200, or by merely listening to clicks as the index mechanism 120 isindexed the appropriate number of teeth, with each tooth movementrepresenting, for example, 10 degrees.

Referring now to FIGS. 29 and 30, once the ideal anteversion isdetermined for the use of the trial in the patient, the clinicallyproven correct anteversion can be measured by use of the instrument 200.Once the trial 100 is set in the proper position, the instrument 200 maybe positioned into the trial 100 and the locking arms moved from itsunlocked position (shown in solid in FIG. 29) to its locked position(shown in phantom in FIG. 29). Once the instrument 200 is locked in adesired setting, this desired setting may be repeated on, for example,an implant by reading the setting on the indicia 254 or by maintainingthe instrument 200 in its locked position and utilizing the instrumentto properly preset an implant or stem prosthesis.

Referring now to FIG. 31, the instrument 200 is shown in position onprosthetic hip stem 51. It should be appreciated that the instrument 200may be similarly used on hip stems 10 of FIGS. 12 through 19. It shouldbe appreciated that the trial 100 and the instrument 200 may also beused be used with monolithic stems. Once the proper anteversion isdetermined by the trial 100 and the instrument 200, a monolithic stemcan be used with that determined anteversion.

Before the instrument 200 is installed onto the hip stem 51, theproximal body 52 is loosely fitted to the distal stem 54 so that theproximal body 52 may rotate in the direction of arrows 226 with respectto the distal stem 54. In this rotatable assembly condition of the hipstem 54, the instrument 200 is engaged with the hip stem 54. Theproximal body 52 will be rotated in the direction of arrow 226 (seeFIGS. 29 and 31) with respect to the distal stem 54 so that the key 204may completely seat into the slot 66 of the distal stem 54 and so thatthe pin 212 may fully seat into the holes 53 in the hip proximal body52. Once the instrument 200 is fully seated into the hip stem 54, thedistal end of the distal stem 54 may be slightly tapped in an upwarddirection to seat the proximal body to hip stem 51.

Since the angle between the axis 83 of the pin 212 and the neckcenterline 85, shown at β in FIG. 31, is fixed, and since the positionof the axis 83 of the pin with respect to the hip stem 54 is set by thelocked instrument 200, the implant can be fixed with the properanteversion angle between the neck centerline 85 and a plane 87 throughthe anterior bow of the stem 56. In this secured and tapped position,the centerline neck centerline forms the prosthetic anteversion angle ααwith the plane 87. Through the use of the instrument 200, the prostheticanteversion angle αα is virtually identical to the trial anteversionangle ααα of the trial. (See FIG. 11) And since the plane 87 willcorrespond with the plane 29 through the anterior bow of the femur (SeeFIGS. 16 and 16A) when the prosthetic is implanted, proper orientationof the prosthetic head and neck can be achieved.

After the proximal body 52 has been seated temporarily into the distalstem 54, instrument 200 may be removed. After removal of the instrument200, the proximal body 54 may be securely seated onto the distal stem 54by utilizing tools (now shown) to finalize the assembly of the stem 51and proximal body 52.

Referring now to FIGS. 32 and 33, an alternate orientation device isshown as orientation device 300. Orientation device 300 is similar toorientation device 200 of FIG. 24. The orientation device 300 includes abody 320 that defines an opening 322. Within the opening 322 is a sleeve334. An orientation rod 324 is slidably fitted to the sleeve 334. Alocking arm 328 selectively locks the sleeve 334 to the body 320. A tang304 on the distal end of the orientation rod 324 may engage a slot 466in the proximal end of the distal stem 454 of hip stem 400. An alignmentfork 310 is slidably and rotatably fitted to the body 320. The alignmentfork 310 engages the sides 453 of the neck 452 of hip stem 400. Whenutilizing the orientation device 300 the locking arm 328 may bepositioned in an unlocked position and the tang 304 angularly adjustedwith respect to alignment fork 310 until the alignment fork and the tangare properly seated into the proximal body 452 and the distal stem 454of the hip stem 400, respectively.

Referring again to FIGS. 22 and 23, the orientation device 300 mayinclude indicia 354 similar to the indicia 254 of the orientation device200 of FIG. 24. The indicia 354 may include a single indicia located onsleeve 334 which cooperates with body indicia 360 on the body 320 toprovide for a measurement of the anteversion of the hip stem 400.

Referring now to FIG. 34, another embodiment of the present invention isassembly 500. Assembly 500 is a combination of the neck trial 106 on theimplant stem 54 of FIG. 1 including, for example, the index mechanism120 and the inner sleeve 164 with distal stem 54 of the hip stem 51 ofFIG. 20. As shown in FIG. 34, the surgeon may place a bowed distal stem54 into the canal 46 of the long bone 16 and proximal body trial 164, aneck trial 106 may be placed on the distal stem implant 54. Theinstrument 200 of FIG. 24 may be placed on the assembly 500 to presetthe anteversion angle prior to a trial reduction or the alignment device200 utilized after a trial reduction has been performed utilizing theassembly 500 to determine the intraoperatively-found ideal anteversionangle so that it can be replicated with a proximal body implant. In thisprocedure, the proximal body implant would be placed on the distal stem54 preferably utilizing the alignment tool 200 and once in properposition, the proximal body implant could be tapped in position. Afterbeing tapped into position, the alignment instrument 200 may be removedand a tool (not shown) may be used to secure the nut 56 to the distalstem 54 to secure the hip prosthesis 51 (See FIG. 21). It should beappreciated that a distal stem trial may likewise be used in conjunctionwith a proximal body implant. The distal stem trials may be smaller thanthe corresponding distal stem implants and thus may be used inconjunction with a proximal body implant to perform the trial reduction.

Referring now to FIG. 35, a kit 666 according to the present inventionis shown. The kit 666 is utilized to prepare a cavity in the femoralcanal of a femur and to assist in performing a trial reduction. The kit666 includes a trial 602 for use in performing joint arthroplasty. Thetrial 602 is to be fitted into a cavity in the canal of a long bone andto assist in performing a trial reduction in performing jointarthroplasty. The kit 666 may further include an instrument 522 for usein determining the selected position of the stem portion of a trial withrespect to the neck portion of a trial and to determine the selectedposition of a stem component to a neck component of a prosthetic stem.The instrument 522 includes a first member 524 of cooperation with theneck component of a implant or a neck portion of a trial. The instrument522 further includes second and third members 526 and 204 forcooperation with a stem portion of a trial and with a stem component ofan implant. The instrument 522 further includes a body 528 foroperatively interconnecting the first member 524 with the second member526. The kit 666 may also include components for assembling one or moreprosthetic components, such as the prosthetic femoral components shownat 612 and 620. Each of the prosthetic femoral components may include aproximal body 614, 624 and a distal stem 616, 624. Sleeves 626 couldalso be included in the kit 666.

Referring now to FIG. 36, a method for providing joint arthroplasty 700is shown. The method 700 includes a step 702 of resecting a long bone.The method 700 further includes a step 704 of preparing a cavity in themedullary canal of a long bone. The method further includes the step 706of providing a trial having a stem portion and neck portion adjustablyfixably connected to the stem portion in a plurality of selectablepositions with respect to the stem portion. The stem portion having afeature to cooperate with a bony landmark of the patient. The methodfurther includes the step 710 of selecting one of a plurality ofselectable positions of the trial. The method further includes step 712of performing a trial reduction using the trial. The method furtherincludes the step 714 of determining an optimal position of the neckportion with respect to the stem portion. The method further includes astep 716 of selecting an implant with the optimum position of the neckwith respect to the stem as determined by the trial reduction. Themethod further includes the step 720 of implanting a selected implantinto the cavity.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions, andalterations can be made therein without departing from the spirit andscope of the present invention as defined by the appended claims.

1. A kit for use in performing joint arthroplasty, said kit comprising: a trial for use in performing joint arthroplasty, said trial to be fitted to a cavity in the canal of a long bone and to assist in performing a trial reduction in performing joint arthroplasty, said trial including a stem portion and a neck portion selectively operably connected to said stem portion in at least three discrete spaced apart positions with respect to said stem portion; an implant for use in performing joint arthroplasty, said implant to be fitted to a cavity in the canal of a long bone and to assist in performing joint arthroplasty, said implant including a stem portion and a proximal body portion selectively operably connected to said stem portion in at least three discrete spaced apart positions with respect to said stem portion; and an alignment device for replicating the alignment of said trial onto said implant, said alignment device adapted to be fitted to said trial at one of said three discrete spaced apart positions and adapted to be fitted to said implant at a corresponding one of said three discrete spaced apart positions, wherein the alignment device includes a first member and a second member that is movable relative to the first member, the alignment device further including a body coupled to the first and second members for at least one of replicating and measuring the relative angular orientation of the stem portion relative to the neck portion, the body further comprising a lock for selectively preventing relative motion between the first member and the second member.
 2. The kit of claim 1, wherein said stem portion comprises a distal stem and a proximal body, said distal stem and proximal body are discrete components and said stem portion comprises an assembly of said discrete components, said proximal body comprises an assembly including a keyed member, spline member, ring and sleeve.
 3. The kit of claim 1, wherein said stem portion has an elongated arcuate rod shaped external periphery, the arcuate rod shaped external periphery conforming to the medullary canal of the femur.
 4. The kit of claim 1: wherein said stem portion defines a longitudinal axis thereof; wherein said neck portion defines an opening therein, the opening defining a longitudinal axis thereof, the longitudinal axis of the opening being coincident with the longitudinal axis of said stem portion; and wherein said neck portion is rotatably connected to said stem portion about the longitudinal axis of said stem portion.
 5. The kit of claim 1, further including a sleeve rotatably positioned on the outer periphery of said stem portion.
 6. The kit of claim 1: further comprising a locating feature associated with said stem portion; wherein said neck portion comprises a second locating feature; and wherein both locating features are accessible from the proximal end of the trial.
 7. The kit of claim 1, wherein said neck portion is fixedly connected to said stem portion by means of an indexing mechanism providing the at least three spaced apart discrete angular positions of said neck portion with respect to said stem portion.
 8. The kit of claim 1, further comprising a resilient connector for connecting said neck portion to said stem portion, said connection including a first set of teeth operably connected to said neck component, a second set of teeth operably connected to said stem component, said first set of teeth and second set of teeth adapted for indexable engagement with each other to provide for a plurality of discrete spaced apart angular positions of said neck component with respect to said stem component, and a spring for biasing said first set of teeth into engagement with said second set of teeth. 